Abrading



L. A. MARTIN Dgc. 16, 1952 ABRADING 3 Sheeqs-Sheet 1 Original Filed May1, 1948 vmwrag law/fence ,q/l/arf/fl WW MXM I Dec. 16, 1952 L. A. MARTIN2,621,450

ABRADING Original Filed May 1, 1948 3 Sheets-Stua-wv 2 Dec. 16, 1952 L.A. MARTIN 2,621,450

ABRAbING Original Filed May 1, 1 948 5 Sheets-Sheet 3 iii . WWMXAirman-'2':

l atented Dec. 16,, 1955 ABRADING Lawrence A. Martin, White BearTownship, Ramsey County, Minn., assignor to Minnesota Mining &Manufacturing Company, St. Paul, Minn., a corporation of DelawareOriginal application May 1, 1948, Serial No.

1952, Serial No. 292,446

1 Claim.

This invention relates to machines for shape grinding, e. g., forgrinding curved surfaces, particularly the edges of relatively thinobjects such as sheets of metal, glass, plastic, wood, stone and othermaterials.

Heretofore such operations have been accomplished by abrasive beltabrading or grinding machines, applying the edge of the work piece alongthe length of the belt and using a backup or contact wheel having aperiphery complementary in shape to the desired contour of the objectbeing abraded. Such arrangements have certain disadvantages. One is thefailure of the belt to bend or curve into exact conformity with theperiphery of the contact wheel, due to the stiffness of the belt and/orthe sharpness of the contours. Another is belt wastage; the margins ofthe belt are usually untouched insuch operations.

Abrasive wheel abrading or grinding machines have also been heretoforeused, the wheel (like the above mentioned belt contact wheel) having ashaped periphery complementary to the desired contour of the objectbeing abraded. A disadvantage of this is the necessity for a differentwheel for each desired shape. Another is wheel wastage. The wheel wearsand loses its desired shape so that it must be discarded if accurategrinding is desired; additionally, the wheel usually wears only alongthe center of its periphery, leaving the edges of the periphery orcorners of the wheel unused.

Objectives of the present invention therefore include the provision orabrading or grinding machines capable of using heavy duty belts orwheels that will produce, grind, abrade and/or polish surfaces of agiven contour on hard materials accurately and with a minimum of belt orwheel waste.

Briefly, the invention provides for bringing the work piece into contactwith a rotating abrasive implement (e. g., a rotating abrasive beltcontact wheel or a rotating abrasive wheel) and at the same time movingthe implement with its axis of rotation always parallel with itself in adirection perpendicular to its axis in a path complementary to thedesired contour.

The invention may be employed to give a square or angular shaped edge acurved shape, or to polish, abrade or otherwise further finish an edgethat is already curved. It may also be employed to form or finish asquare or straight edge.

As illustrative embodiments, an abrasive belt machine and an abrasivewheel machine for the Divided and this application June 9,

edge grinding of sheets of glass are described below and illustrated inthe accompanying drawings in which:

Figure 1 is a side elevation of an abrasive belt machine with a portionof the frame broken away;

Figure 2 is a front elevation;

Figure 3 is a plan view of the forward portion;

Figure 3a is a greatly enlarged fragment of the sectional view of one ofthe two circular oscillator plates that appears in Figure 3, to show theshims;

Figure 4 is an enlarged side elevation of the oscillator;

Figure 5 is a diagram showing relative movements of certain parts;

Figure 6 is a side elevation of an abrasive wheel machine;

Figures 7, 8 and 9 are diagrams of alternative forms; and

Figures 10, ll, 12, 13 and 14 show various edge shapes that can beground on the illustrated machines.

Three pulleys ll, l2 and I3 support an endless abrasive belt I4 (Figures1 to 5). The belt is driven by the driving pulley II which in turn isdriven or rotated by a motor 15 through a driving belt Hi.

The pulley l2, which is the contact roll or wheel, is rotatably mountedon a spindle or journal l9 that is fixed in a reciprocator oroscillator. The oscillator comprises two vertical parallel circularplates 20 and 29' connected by a spacer bar or girder 2|. A stationarycradle is formed of two upright frames 22 and 22' having circularopenings with inside circular tracks that are shaped to make a slidingfit with the peripheries of the plates so as to support the oscillatorin a manner to permit oscillating it about its horizontal axis 23. Thesaid axis is indicated by the point 23 in Figure 4, and is sometimesreferred to herein as the axis of oscillation.

For ease of assembly and future adjustment for wear, both of the plates29-20 have V-shaped peripheries and are split radially into two halvesl2ll-l2ll' and 228-220 along the groove of the V with a number of verythin sheets 8-8 or" metal inserted between the halves to serve as shims.Removal of a shim permits the two halves of a plate to be drawn closertogether and thus take up peripheral wear.

The contact wheel I2 is rotatably mounted on the outer or right handsurface of the oscillating plate 20 with its axis parallel with the axisof oscillation. The spindle i9 is adjustably fixed in the plate so thatit may be moved toward or away from the axis 23, as desired. Theperiphery of the contact wheel [2 is normally positioned slightly belowthe axis of oscillation.

The plates Eli-29' are cut away about their centers and a sector isremoved from their upper portions to permit passage through theoscillator of a work piece 2d along a guide groove that is cut in aguide bar or rack 26. The plates are thus, in effect, crescent shaped,with their outer peripheries sliding in the circular tracks in theupright cradle frames 22-22.

The oscillator assembly is oscillated about its axis 23 by an arm 21which is fixed to the spacer 21 of the assembly and is moved up and downby a pitman 28. The pitman is operated by a crank wheel 29 which isrotated through a worm gear assembly 36 by a motor 3!. Such anarrangement produces an advantageous variable speed oscillation. Whenthe contact wheel 12 is at the center of its oscillation, the pitman ismidway of its downward (or upward) travel (Figure 1) and is moving atits fastest rate of speed. As the pitman nears the end of its stroke,its speed gradually slackens until it reaches zero at the turning point.The result is that when contacting the center of the glass where only alittle abrasion is needed, the oscillating movement of the contact wheel32 is rapid and it passes quickly over the area; but when contacting thecorners where the grinding is heavy, the movement is slow and thecontact wheel thus dwells longest where it is most needed.

When the oscillator 20-20 is oscillated about its axis 23 in the cradle'2222, the rapidly spinning contact wheel 12 is reciprocated with itsaxis always parallel with itself (i. e., with its axis always parallelwith its immediately previous position) in a direction perpendicular toits axis, in a path complementary to the surface being formed or ground.The contact point or contact line of the wheel [2 will reciprocate oroscillate in a circular path about the axis of oscillation 23, and thelower edge of the work piece 25 will be ground to a shape complementaryto the said path, i. e., the piece will be given a cylindrical edge, i.e., a convex rounded edge that is circular in cross section such as isshown in Figure 10 or 11 (sometimes called a pencil edge). The axis ofoscillation 23 lies wholly within the guide groove 25. The bottom of thegroove is below the axis so that the bottom edge of the work piece 24will contact the abrasive belt I4 on the contact wheel I2 when the workpiece is advanced through the machine along the path defined by thegroove. The path of the object lies within a plane that is determined bythe axis of oscillation and that at the same time is always parallelwith the axis of the contact wheel H.

To compensate for the movement of the abrasive belt l4 that is caused bythe oscillation of the contact wheel I2, and to keep the belt taut, theidler pulley I3 is rotatably mounted on an upright arm which is pivotedat 35. A horizontal arm 31 extending from the arm 35 is impelleddownwardly by a spring 38, whereby the upright arm 35 and with it thepulley i3 is impelled forwardly to maintain a desired tension on theabrasive belt M. The spring yields when the pulley i3 is impelledrearwardly by the belt when the contact wheel l2 moves from its centerposition toward either extremity of its oscillation.

Positional adjustment of the idler pulley l3 4 may be made by moving thebed plate 49 which supports the arm 35, rearwardly or forwardly by thescrew assembly 4!.

Where it is desired to use an abrasive wheel as the abrading implementrather than an abrasive belt, the contact wheel 12 of the described beltmachine may be replaced by an abrasive wheel H2 and a driven pulley ill,both fixed to each other and journaled on the spindle 19 (Figure 6). Theillustrated abrasive belt I4 would then be replaced by a power ordriving belt I 14 which would drive the pulley H7 and thereby rotate theabrasive wheel H2. The operation and construction would otherwise be asherein described in connection with the use of an abrasive belt, withthe wheel H2 swinging or oscillating about the axis 23 in the samemanner as the abrasive belt contact wheel 12 so as to abrade the loweredge of the work piece 24. A single machine could thus be equipped withinterchangeable parts so as to employ either an abrasive belt or anabrasive wheel, as desired.

It will thus be seen that the invention involves certain prescribedmovements of what may accurately be termed rotating abrasive implements.

The illustrative examples of a rotating abrasive implement that arespecifically described and illustrated herein are (1) an abrasive beltthat is supported by the periphery of a contact wheel (which may also bedescribed as a contact wheel carrying on its periphery an abrasive belt)and (2) an abrasive wheel. These two examples, in turn, may accuratelybe termed abrasive surfaced wheels.

Other implements that abrade by being rotated about their own axes withtheir peripheries in contact with the work, are also contemplated by theinvention.

The abrasive wheel l l2 may be a solid abrasive wheel or it may comprisea non-abrasive core coated on its periphery with a layer or thickness ofabrasive substance. The term abrasive wheel as used herein, is intendedto embrace both.

Numerous other alternatives and equivalents may be employed that embodythe principles of the invention.

The construction of the oscillator may vary. For example, it couldcomprise a single plate, such as the plate 28, and such plate (or bothplates if there are two) may be of a shape or design other than thatillustrated as long as it will clear the work that is being passedthrough the machine and oscillate the contact wheel about an axisparallel with the axis of the wheel.

The path of reciprocation or oscillation of the contact wheel 12 hereshown as circular, may follow the contour of other desired shapes, e.g., of an oval, an ellipse, a compound curve, a reverse curve, etc. Alsothe path may be straight, if desired. The non-circular curved shapes areusually used in connection with work pieces that are relatively thick.

Apparatus suitable for producing reciprocations or oscillations of thecontact wheel in paths other than circular is shown in diagram in Figure7. The abrasive belt contact roll l2 rotates on a journal i9 which isslidably held in a slot 45 that is cut in a stationary bearing plate 45.The journal [9' and with it the contact wheel i2 is reciprocated in theslot by a crank 29 and pitman 28. The slot 45, here shown as of a noncircular curved shape, may be of any desired shape. Its shape will bereproduced on the surface or edge of the work piece 2 3 being ground.

For example, if the slot is a portion of an ellipse. the piece will begiven a cylindroid edge, i. e., a convex rounded edge that is ellipticalin cross section. If the slot is straight, as shown in Figure 8, thepiece will be given a straight edge, such as the square edge shown inFigure 14. If the slot has a downward curve such as shown in Figure 9,the piece will be given a. concave edge such as shown in Figure 13.

When the path of reciprocation is circular, as in the machine shown inFigures 1 to 5, the edges of work pieces will variously appear as shownin Figures 10, 11 and 12, depending on the distance between the contactwheel and axis of oscillation 23. In forming the edge shown in Figurethe point or line of abrasive contact was below the axis a distanceequal to half the thickness of the work piece, and the resultant edge issemi-circular in cross section; in Figure 11 the point of abrasivecontact was below the axis more than half the said thickness; and inFigure 12 the point of abrasive contact and the axis of oscillationcoincided. Holding the contact wheel at one point without reciprocationwill produce a concave edge such as that shown in Figure 13.

The path of movement of the work piece here shown as being along theaxis of oscillation in a straight line to accommodate the straight edgeof the illustrated work piece, may be curved in respect to horizontal toaccommodate a work piece having a curved edge, such as automobile windowglass, and yet still be straight in respect to vertical. It would liewithin a plane that is determined by the axis of oscillation. Such apath is still regarded as being along the axis of oscillation within themeaning of that phrase as used herein.

It will be understood that the terms vertical, horizontal, front, back,top, upper, upright, etc. are relative and not limiting, because theillustrated machines that here show the work piece in a verticalposition with the edge that is being ground in a horizontal position,may be constructed and/or positioned so that the work piece would be,for example, horisaonltal or the edge being ground would be vericaMachines may of course be constructed of any size. The illustrativemachine shown in Figures 1 to 5 has an abrasive belt contact wheel I2measuring 5" x 5" and it has successfully'produced and finished edges onsheets of glass ranging in thickness from A" to A".

The use of the full width of the abrasive belt of life. Belts usedaccording to the present invention for the edge grindling of sheets ofglass have been found to possess at least ten times the life of the samebelts when used in machines and methods heretofore known. Consequently,the abrasive belt machine and method provided by this invention is farsuperior to any means for the edge finishing of glass heretofore known.

The abrading of objects of all kinds, made of a variety of materials aspreviously mentioned,

is contemplated. Such objects include glass doors, automobile windowglass, marble slabs, laminated wood, plastic sheets, etc.

The examples herein show the abrading of the narrow surfaces ofrelatively thin objects, such narrow surfaces commonly being called the"edges." The abrading of other types of surfaces, however. is alsocontemplated. For example, the edges of an article such as a sheet ofglass, may be beveled by tipping the sheet at an angle and abrading thecorners of the edge; 1. e., where the broad surfaces of the glass andthe narrow edge surface meet.

This application is a division of the copending application'of LawrenceA. Martin, Theodore J. Miller and Lluellynn A. Wright Serial No. 24,486filed May 1, 1948.

Iclaim:

In an abrasive belt machine for abrading an edge of a sheet of glass; aplurality of pulleys for supporting an endless abrasive belt, one of thepulleys serving as a contact wheel; means for rotatably mounting thepulleys; means for reciprocating the contact wheel mounting in adirection perpendicular to the wheels axi with the said axis alwaysparallel with itself; and guide means for maintaining a sheet of glassin a plane that is parallel with the wheel's axis and for conducting thesheet across the width of the belt where the belt is trained around thecontact wheel in a path lying along an edge of the sheet with the edgein position to contact the belt.

LAWRENCE A. MARTIN.

No references cited.

